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The main purpose of Daylight Saving Time is to make better use of daylight. We change our clocks during the summer months to move an hour of daylight from the morning to the evening.
The rationale behind Daylight Saving Time is to save energy in the summer months by extending the daylight in the evening when more people would be using more lights and electricity.
Daylight Saving Time was conceived by Benjamin Franklin in 1784. Then in 1907, Englishman William Willett advocated Daylight Saving Time in the pamphlet, "Waste of Daylight" where he wrote:
"Everyone appreciates the long, light evenings. Everyone laments their shortage as Autumn approaches; and everyone has given utterance to regret that the clear, bright light of an early morning during Spring and Summer months is so seldom seen or used."
Countries all over the world have set Daylight Saving Time for various reasons, including in times of war, and times of economic struggles to save on energy. There are those who are opposed to it and there are regions and countries that have used it and discontinued it. Throughout the past century, many countries, including the U.S. have had inconsistancies with Daylight Saving Time with lax laws and difficulties with the different regions setting different times. Britain was the first country to set the time throughout a region to one standard time. America set the Uniform Time Act of 1966 (15 U.S. Code Section 260a) to standardize the time between the regions. The law does not require that anyone observe Daylight Saving Time; all the law says is that if we are going to observe Daylight Saving Time, it must be done uniformly.
The U.S. and Canada did not even have Standard time in time zones established until 1883 which was established by U.S. Law with the Standard Time Act of 1918. This act also set a Daylight Saving Time which was repealed the following year, re-established during WWII and continued nationally thru 1945. After the war, it varied among the states and regions and become confusing without any standards in place specifically for Daylight Savings. The Uniform Time Act of 1966 (15 U.S. Code Section 260a) standardized the dates for starting and ending Daylight Saving Time. It does not require that anyone observe Daylight Saving Time and provides for exemptions from its observance by the states, but states that if it is observed, it must be done uniformly.
The U.S. state and territories that do no observe Daylight Saving Time is Arizona, Hawaii, American Samoa, Guam, Puerto Rico, the Virgin Islands, the Commonwealth of Northern Mariana Islands. The Navajo Nation participates in the Daylight Saving Time policy, even in Arizona, due to its large size and location in three states.
It has changed in start and end times several times since and in 2007 it was extended one month in the U.S. to change at 2am and begin on the second Sunday of March and end on the first Sunday of November.
Approximately 70 countries around the world use Daylight Saving Time. Some places refer to Daylight Saving Time as "Summer Time" as it is the summer months when the time is changed to move an hour of daylight from the morning to the evening. Countries around the world use Daylight Saving Time at dates that are established for their purposes. Many countries have established and then discontinued Daylight Savings.Areas that are closer to the North or South Poles generally have longer periods of daylight in the summer and do not typically change their clock. Likewise, countries closer to the equator where daylight hours are similar during every season, also do not typically observe Daylight Saving Time.
Japan, India, and China are the only major industrialized countries that do not observe daylight saving.
European nations, after decades of observing some form of Daylight Saving Time, in 1996 the European Union (EU) standardized an EU-wide "Summertime Period." The EU version of Daylight Saving Time runs from the last Sunday in March through the last Sunday in October. Iceland observes the Western European time zone year round and does not change its clocks.
In the European Union, all time zones change at the same moment. Summer Time begins and ends at 1:00 a.m. Universal Time (Greenwich Mean Time). It begins the last Sunday in March and ends on the last Sunday in October.
It begins the last Sunday in March
ends the last Sunday in October